Wind-Speed Software on New Tack

With today’s emphasis on alternative energies, a software program from APL could soon be in high demand by those planning wind farms in coastal waters. The Space Department’s Francis Monaldo is leading a project to create an operational version of the software, which automatically converts satellite imagery into high-resolution maps of wind speed over water.

The project, which began as a research effort for the National Oceanographic and Atmospheric Administration (NOAA) in 1999, offers significant improvements over existing technologies. “We get very high resolution, anywhere from 25 meters to a kilometer. Other systems are on the order of 12 to 25 kilometers,” says Monaldo.

The APL/NOAA SAR Wind Retrieval System (ANSWRS) relies on data from synthetic aperture radar (SAR) systems on satellites to determine wind speeds of 0–20 meters per second (0–45 mph). The fine resolution is especially important in coastal waters where wind farms are being built because land features can create very local changes in wind patterns.

The radar emits pulses, which reflect off of the sea below. “The rougher the water, the more energy comes back to the radar,” explains Monaldo. “The higher the wind speed, the rougher the ocean’s surface and the brighter it appears in a radar image.”

The radar can penetrate clouds, so weather does not get in the way of data collection. NOAA gets the SAR data from a number of satellites: Canada’s RADARSAT-2, the European Space Agency’s Envisat, Germany’s TerraSAR-X, and Italy’s COSMO-SkyMed.

The variety of satellites poses no problem for ANSWRS, says Monaldo. “We’re creating what’s called an ‘ingestor’ for the operational system. It can take SAR data from different sources and put it in the same format. We’re also going to produce intermediary products, which will make the system useful for a wider variety of applications.”

The system provides near-real-time processing of the SAR data as they are acquired by the satellites and transmitted to APL, but it can also be used to understand a location’s past. “You can go back and apply our algorithms to the raw data already out there and develop a climatology [weather conditions averaged over a period of time] for that location,” says Monaldo.

With the help of APL’s Office of Technology Transfer, the research version of the software has already been licensed to the Risø National Laboratory for Sustainable Energy at the Technical University of Denmark, which is using the software to identify the best locations for wind farms. The software can also help determine the ideal placement of individual turbines, says Monaldo, because one turbine could adversely affect the wind flowing toward another.

A 2008 APL intern from the Technical University of Denmark, M. Bruun Christiansen, worked with Monaldo and Donald Thompson to develop methods to apply the software to wind-farm planning. The university is also using ANSWRS to contribute to a United Nations solar and wind energy resources assessment project in the United Arab Emirates.

“We’re excited,” says Monaldo. “We’re moving from cool science to operations, and now with our planned intermediary products, ANSWRS could be used for different applications such as ship detection, checking on oil platforms after a storm, or tracking the extent of an oil slick, which tends to smooth the water’s surface.”